The majority of deaths from cancer following chemotherapy and remission result from recurrence of the original treated tumor or tumors. This appears to be somewhat counterintuitive, as known cancer therapies sometimes, but do not always, eliminate tumors to the point where a patient may be declared “cured.”
A theory that has been advanced to explain the recurrence of tumors, as well as tumor growth per se, is the “cancer stem cell” or “CSC” theory. In brief, this theory posits that a rare population of cancer cells which possess some characteristics of stem cells undergo asymmetric division which in turn leads to replacement stem cells, and to more lineage restricted populations of tumor amplifying cells. These “new” cells proliferate rapidly, and make up the majority of the tumor, in contrast to the stem cells, which are slow-cycling, quiescent, and are resistant to therapies which target rapidly dividing cells. The result of this is that while the majority of cells in a tumor are susceptible to one or more of these targeted therapies, the small population of stem cell-like, chemo-resistant cancer cells, are not destroyed, and the cycle discussed supra repeats itself.
Clearly, there is a need to identify these stem cell-like cancer cells, as well as a need to quantify their presence in tumors of a particular subject or patient. Also, while the field of oncology recognizes a number of chemotherapies for cancer “one size does not fit all,” and a need remains for developing targeted therapies, as well as a more general method for identifying potentially useful anti-tumor drugs.
U.S. Pat. Nos. 5,888,497; 6,303,151; 6,808,705; 6,818,230; 7,041,504; and 7,297,331, all of which are incorporated by reference in their entirety, describe methods for encapsulating cancer cells in agarose beads, which are in turn coated with agarose. The type of agarose may vary, as shown in the context of other cell types (islets), as per, e.g., published application 2007/0071732, also incorporated by reference in its entirety.
Work on these encapsulates of cancer cells has led to the observation that populations of cells develop which might possess properties paralleling stem cells. It was thus of interest to determine if the materials described in these references could be used to isolate chemotherapy resistant cancer cells, which also possess stem cell-like properties. In so doing, it was also learned that these encapsulates could be used to screen compounds of interest to determine if the compound is efficacious against cancers.
How these and other aspects of the invention are achieved will be seen in the disclosure which follows.